Sins of the Mortals (Nanatsu no Taizai X Highschool dxd
by NewOtaku
Summary: The Heavenly Dragons are dangerous, but no being but the Infinity dragon and Big Red can out class the Sins of the Humans. Sealed in their own Sacred Treasures by God, the Sins trains their hosts to fight for the balance in the realms and to protect the humans from the hands of the supernatural.


Sin of the Mortals

Prologue

"Onee-chan can you tell us a story?" asked a young girl

"Which one?" A Devil King asked

"About a powerful hero!" Screamed a young red head girl

"Okay I have a story, story about heroes of the humans" the Devil king replied.

"During the ancient times of the realms, war and conflict engulfed the Earth; war between the Three factions, the conflict of the Heavenly Dragons, and the abuse of every faction to the humans spilled mortal blood to the earth. The Biblical God saw His children in pain and invented the sacred gears to protect themselves, but the supernatural used this inventions to their advantage which continued the abuse.

When blood continued to pour, the King of Liones possessor of the a sacred gear to see the future saw seven criminals fighting for the salvation of the mortals, once the vision finished he summoned his knights to gather the figures in his vision. His knights looked every corner for the individuals the King described. It took blood, sweat, tears and time to look for them within the continuous conflict and in six months of searching, they found them.

The King named them, Nanatsu no Taizai. Seven knights who represent each Sin."

"Knights who represent sin… so they're devils?" the black hair girl asked.

"No, well, one of them is. The knights consist of different species"

"So why do they serve the humans?" asked the red haired

"We don't know…, but going back. They defeated any supernatural being that is a threat to the humans. They killed many beings who abuse the humans and it affected the War. What was shocking was the knight who represent Wrath knocked out the Heavenly Dragons when they were clashing near a village." The Devil King said with awe

"What! Ddraig and Ablion fell by the Seven Deadly Sins!?" the girls yelled in disbelief

"No… only one of them did. The Sin of Wrath" the Devil King said in a stern voice.

The girl simply didn't say a thing but imagine the might of the Sin of Wrath.

"Wait so if one of them can take on the Heavenly Dragons, so technically all seven can wipe out all of the factions!" the girl with black hair exclaimed

"Yes… and they nearly did, the Sin of Envy defeated the Titans of Olympus, the Sin of Lust traumatized the God Loki" the Devil King said with a scared and awed toned. "Heracles was given a labour to take out one of them, his 13th labour you can call it, but their battle with the Sin of Pride didn't last a minute, only leaving Heracles in ashes."

The girls were know scared of these knights of what they can do, they are starting to see them as monsters that must be taken down.

"But they all did that to protect the weak." The Devil King reassured "They protected the weak mortals which the elders disregard as insects or fondle."

"So what happened to them?" the red haired girl askes.

"All of the patheons and factions gathered in a hall to discuss about the Sins. The Christian Patheon, Norse, Greek, Shinto, the Dragons and all of the Supernatural beings wanted to dispose them." The Devil king continued. "They all planned to simply eliminating them by attack their home kingdom with all of magic that ever existed. It was a simple plan, but they thought that all of the might of the gods and the Heavenly Dragons can take them out. When the spies informed them that the Sins were home, they made their move and blasted all their magic in a small area which was their kingdom's castle. The impact created an explosion which eliminated the entire Island of Britania destroying neighboring kingdoms and villages."

"When the dust cleared, the gods were shocked to see the Sins protected by two barriers. They were on their knees at the sight of destruction. The sun gods like Apollo immediately launched a beam of fire towards the Sins, when it made impact it exploded turning everything within a mile to molten rock. But when the dust cleared again, they were again shocked when they saw the Sin of Pride grew in size and used his body to protect the other Sins. Immediately Ablion absorbed the Sins remaining mana and God of the Bible immediately sealed them in sacred gears. All of the patheons agreed to lock them out in the deepest depths of Hades' world with all of the magic in the world." The Devil Kings told approaching to the conclusion of the story.

"When they were gone, the world continued to turn, and the humans continued to suffer" The Devil King ended the story.

Then a magic circle appeared and Sirzechs appeared

"Onii-chan!" Rias exclaimed

"Hey Rias-tan!" exclaimed the brother of Rias

"Onii-chan, Onee-san Serafall told us a story about the Seven Deadly Sins! They are so powerful!" Rias exclaimed in awe and wonder.

"Ohh she did. Well they are powerful in their own ability" Sirzechs said and carried the young Rias as they prepare to leave the room.

"Say your goodbyes Rias-tan" Sirzechs said

"Bye Sona, bye Serafell" Rias waved before a flash of crimson light appeared and teleported them out of the room leaving

Sona looked at her Onee-san with a fearful expression and asked: "Onee-san, they are not real right?"

But Serafall didn't respond and was lost in her own thoughts. "Onee-san?" Sona asked worried for her sister.

Serafall flinched and simply smiled at her little imouto and said with a bright smile: "Ohhh… they are just friction, more like a folktale for the supernatural."

Sona just smiled brighty at her response and hugged her onee-san and said: "Wow, they are really strong, well I guess they were just written to be strong." While rubbing her face to Serafall's chest.

Serafall just smiled at her sister's actions and had a sad smile as a memory flashed before her eyes.

_**Flashback**_

All the factions stared at the Sins with worry as they stare at the glares of the Sins piecing their very existence as they Vanish from their sight.

_**End of flashback**_

"_Atleast we will never see you again, Sins" _Serafall thought.


End file.
